The present invention relates to a PDA antenna adapted for use in a portable communication terminal called a PDA (Personal Digital Assistants).
Up to the present time, many kinds of relatively small portable communication terminals called PDA have been put into use. Such PDAs can process digital information with respect to letters, images or sounds and provide such functions as wireless data communication and telephone communication and xe2x80x9ctouch inputxe2x80x9d or xe2x80x9cpen inputxe2x80x9d functions.
FIG. 9 is a perspective view showing a PDA provided with a conventional PDA antenna. FIG. 10 is a side view showing a PDA provided with a conventional PDA antenna. FIG. 11 is a side view showing a PDA in the course of telephone communication. FIG. 12 is a perspective view showing a PDA in the course of data communication. FIG. 13 is a perspective view showing a PDA with a built-in loop antenna.
In FIGS. 9-13, reference numeral 31 is the body of a PDA, 32 is a display screen showing letters and images and provided with a xe2x80x9ctouch inputxe2x80x9d function, 33 is a microphone for inputting sounds and 34 is a speaker for outputting sounds. The display screen 32, microphone 33 and speaker 34 are provided on the front surface of the body 31.
35 is an extendable/storable antenna used for telephone communication or data communication and capable of being extended from or stored in the body 31. L1 is the distance from the center axis of the antenna 35 to the front surface of the body 31, L2 is the distance from the center axis of the extendable/storable antenna 35 to the back surface of the body 31 and is constructed so that L1 greater than L2. This construction is due to the fact that it is necessary to ensure the gain of the antenna by locating the extendable/storable antenna 35 as far as possible from the user""s face 36 which interferes with the electronic waves as shown in FIG. 11.
37 is a built-in auxiliary antenna maintaining high gain when the gain of the extendable/storable antenna is greatly reduced due to the presence of some kind of interference obstacle.
An electrostatic capacity sensor (not shown) which detects interference obstacles and an antenna switching switch (not shown) which switches antennas between the extendable/storable antenna 35 and the built-in antenna 37 are also provided in the body 31. Their method of application is similar to that used in the wireless telephone device disclosed for example in JP-A-6-21863.
Furthermore, in FIGS. 12 and 13, 38 is an interference obstacle such as a desk mounting the body 31 during data communication for example.
In FIG. 13, 39 is a loop antenna forming the above-mentioned built-in antenna 37 in loop shape.
The operation of the invention will now be explained.
When talking on the telephone, the user holds the body 31 of the PDA in their hand, speaks into the microphone 33 and hears received sounds from the speaker 34 as shown in FIG. 11. Subsequently the extendable/storable antenna 35 is extended to a fixed length from the body 31. This ensures optimal communication conditions as does the fact that when the gain of the extendable/storable antenna is greatly reduced due to the existence of an interference obstacle, the antenna switching switch (not shown) automatically switches the built-in antenna 37 or the loop antenna 39.
Otherwise during data communication, as shown in FIGS. 12 and 13, the user mounts the body 31 of the PDA on an interference obstacle 38 such as a desk and using the display screen, inputs, confirms and communicates data.
Conventional antenna devices used in conjunction with PDAs are constructed as above. Although it is easy to ensure a determined antenna gain when communicating by telephone, when the body 31 is placed on an interference obstacle 38 when communicating data, the distance between the extendable/storable antenna 35 and the interference obstacle 38 reduces to L2, the gain of the extendable/storable antenna 35 is reduced and the reliability of the data communication is reduced.
Furthermore it is difficult to ensure sufficient antenna reliability of the built-in antenna 37 or the loop antenna 39 which should supplement reduced gain of the extendable/storable antenna 35. This is due to such factors as the distance from the interference obstacle 38 or the material constituting the interference obstacle 38 (for instance whether it is metal or not). Also the decision standard for switching the antennas becomes complicated due to the fact that the sensing means for the interference obstacle 38 is dependent on the material constituting the interference obstacle 38.
It is an object of the present invention to solve the above problems by the provision of a PDA antenna device which can easily ensure improved and stable antenna reliability irrespective of such use conditions as telephone or data communication.
The present invention comprises a first antenna used in a first use condition, a second antenna used in a second use condition, a control part which discriminates between the first and second conditions and outputs a discrimination signal and a antenna selection device which selects which of the first and second antennas to use on the basis of the discrimination signal from the control part and connects the selected antenna to the wireless circuit. The invention is adapted to select and use the optimal antenna for each use condition. By such a process, it is possible to easily obtain the discrimination of use conditions and ensure improved and stable antenna reliability irrespective of use conditions.
Further the invention comprises an antenna used in a first and second use condition, a first conforming circuit conforming to a first use condition, a second conforming circuit conforming to a second use condition, a control part which discriminates between the first and second use conditions and outputs a discriminating signal and a conforming circuit selecting device which selects which of the first and second conforming circuits to use on the basis of the discriminating signal from the control part and connects the selected antenna to the wireless circuit through the selected conforming circuit. Thus the invention is adapted to use an antenna by selecting the optimal conforming circuit for each use condition. Hence discrimination of use conditions can easily be obtained, and optimal conformance to each use condition as well as improved and stable antenna reliability can be easily ensured.
The use conditions of the PDA comprise at least data communication, telephone communication, data communication/telephone communication carrying out data communication and telephone communication, and data processing comprising the processing of fixed data before data communication or data communication/telephone communication. Telephone communication is a first use condition, data communication and data communication/telephone communication is a second use condition, and data processing is a first or second use condition. In such a way, it is possible to obtain optimum antenna reliability corresponding to various use conditions.
In the present invention, the second antenna is formed in a bar shape adjustable at least with respect to one of the angle to or the direction from the interference obstacle. In such a way, by this simple structure it is possible to ensure the improved reliability of the second antenna.
The invention provides for the storage of the second antenna in the body. As a result it is possible to prevent the second antenna from projecting from the body and hindering portability when the PDA is carried.
The present invention provides for an antenna installation cover on the body which can optionally change its orientation with respect to the interference obstacle. The second antenna may be provided on the rear surface or in the interior of the antenna installation cover. In such a way, optimal orientation of the second antenna can be easily ensured with respect to the interference obstacle by the optional changing of the orientation of the antenna installation cover and so improved and stable antenna reliability can be ensured.
The second antenna of the present invention is formed with respect to the antenna installation cover by printing, deposition or transferal. Hence it is possible to easily form an extremely thin second antenna and this contributes to the small size and weight of the PDA.
The present invention further provides for a second antenna on one part of the body which optionally changes its orientation with respect to the interference obstacle. A second antenna for the PDA function has been provided by using an indispensable part of the body. In order to provide the antenna a separate member is no longer necessary. This allows a reduction in the number of parts, the simplification of the structure of the PDA unit and a reduction in its weight.
Further the second antenna is formed by printing, deposition or transferal on a part of the body. In such a way an extremely thin second antenna can be easily formed and the size and weight of the PDA can be reduced.
The present invention provides a control part having an orientation sensor which detects the orientation of the body in order to discriminate between a first and second use condition. In such a way it is possible to automatically discriminate the use condition.